As it is known by the man skilled in the art, a traditional architecture to provide content distribution services, such as VOD services to Internet-connected users, is a Client-Server architecture in which users (clients) download the desired content(s) from a server managed by a service provider and connected to a communication network.
More recently, solutions based on a peer-to-peer (P2P) approach have been developed. In the first generation of such peer-to-peer solutions the users were only authorized to store the content(s) they download for their own use, on a temporary basis. As a result, users might download a content of interest only from other users currently consuming the same content, or from the content servers.
In the last few years, a more powerful peer-to-peer architecture has been proposed. In this architecture, users can proactively download content(s) that they are not immediately interested in, but that they might serve to other interested users in the future. This architecture is intended for reducing the amount of infrastructure (server) resources that is required to meet a target quality of service, and hence for reducing the overall cost of infrastructure deployment.
This last architecture can be used, for instance, in the two following specific contexts.
In an “open Internet” context (or open uncontrolled environment), users interact with one another and with the infrastructure servers via their personal computers (or more generally communication equipments) that are connected to the Internet. So, a proactive storage of content(s), managed by the users themselves, can be easily done on the hard disk of the user's personal computer (or equipment).
In an “edge device network” context, the interacting components are either home gateways (connected through DSL or cable) or set-top boxes (STBs) that are located in the user's home premises. In this context, all the edge devices can be controlled by the Internet service provider(s) (ISP(s)) to which the users subscribe. So a proactive storage of content(s) can be done on hard disks of these edge devices.
To reap all the benefits of the last mentioned P2P architecture, it is critical to make adequate decisions regarding which content to proactively store, and where to store it. This issue has been notably considered in the article of K. Suh et al., “Push-to-Peer Video-on-Demand system: design and evaluation”, IEEE Journal in Selected Areas in Communications, December 2007. In this article two strategies have been proposed, namely the “full striping” and the “coding based” placement strategies. These strategies achieve optimal performance but only when the same amount of data is stored for each content and when no information is available on user's preferences.
The prior art document WO 2007/080345 (Thomson Licensing) discloses a multimedia content delivery method and system. The method disclosed in this prior PCT patent application comprises:                a first step comprising a download in “push” mode of a multimedia content, in a partial way, from a content server to a first client device, and        a second step comprising a download of the missing elements of said multimedia content in “pull” mode via a “peer to peer” mechanism from a second client device.        